A cholesteric liquid crystal display is sensitive to external stresses, such as applied pressure or mechanical deformations. The external stress locally changes the gap between the substrates of the display device causing the material flow to spread far from the point of applied stress. Because of the anisotropy in the viscosity of the cholesteric liquid crystal, flow in the gap between substrates creates the planar texture. As a result, the cholesteric display device reflects colored light where the surface of the display is touched and a slight pressure applied. The effect is significantly pronounced when the display is assembled from flexible substrates. Pressure sensitivity can be largely eliminated in a cholesteric display with the use of polymer dispersions where the liquid crystal is encapsulated in the form of droplets within a polymer (see for example U.S. Pat. Nos. 6,061,107 and 7,351,506).
Reduced pressure sensitivity of cholesteric liquid crystals, however, can be utilized to create a writing tablet. Pressure of a stylus on a flexible substrate creates a planar texture image on a focal conic background as described in U.S. Pat. No. 6,104,448. In this application the pressure sensitivity of the cholesteric liquid is limited by the polymer network structure so that the sensitivity to the stylus is controlled, enabling one to trace a well defined line (see U.S. Patent Application Publications 2009/0033811 and 2009/0096942, which are incorporated herein by reference in their entireties). As described in patent publication 2009/0033811, polymer networks are employed to reduce the pressure sensitivity of a cholesteric material so that the pressure created from the tip of a stylus can produce a high resolution image whereas the diffuse pressure of say the hand holding the stylus, does not destroy the image when resting on the display surface. It would be advantageous to develop a writing tablet that employs cholesteric liquid crystal material but does not need polymer in the liquid crystal material to restrict its flow and to provide suitable resolution of the image, when writing pressure is applied to the writing tablet.